This invention relates to a control mechanism for a coupling device, such as a clutch, a speed variator, or a brake, the state of which is modified as a function of the position of a movable train which is movable in both directions through a stroke defined between two limit positions, this train comprising elastic return means in a first of its two limit positions, whilst opposing means associated with the train is movable through a stroke corresponding, position by position, to that of the train and is adapted to act upon the train in order to transfer the latter from its first limit position into its second limit position and vice versa.
This is particularly the case in clutches where, for example, a friction disc is adapted to be clamped between a reaction plate and a pressure plate by the action of a spring, generally in the form of a diaphragm. The clutch occupies the engaged state by the elastic action of the diaphragm which, bearing against a cover connected to the reaction plate, exerts an elastic clamping action upon the pressure plate.
The clutch is transferred from this state of engagement into a state of disengagement by the action of the opposing means which acts upon the movable train formed by the pressure plate and the diaphragm.
This means generally comprises a stop movable in translation, called the clutch release bearing, which acts upon a central part of the diaphragm in order to cancel at will the elastic clamping action of the diaphragm upon the pressure plate. The means comprises, apart from this release bearing, a kinematic chain which generally consists of a fork, levers, rods et cetera.
The means may be operated either manually, such as by a clutch disengaging pedal, or by automatic means.
The operative means generally make the opposing means act upon the train by the effect of a force. If this force is zero or weaker than that of the diaphragm, the clutch is in the totally or partially disengaged state. If, on the other hand, the operating force preponderates over that of the diaphragm, the clutch is transferred into the disengaged state.
In the case of a manual control mechanism where the opposing means is actuated from a clutch disengaging pedal, the driver can, as sensitively as he desires, transfer the train from its first limit position of engagement into its second limit position of disengagement and vice versa, by modulating the force exerted by his foot upon the pedal.
In the case of an automatic control mechanism, the opposing means is generally subject to an operative means acting by the effect of a force which is either in play or out of play.
In the inactive condition of the automatic operative means by the effect of force, the clutch is engaged. In the active condition of this automatic operative means by the effect of force, the means overcomes the elastic resistance exerted by the diaphragm and transfers the clutch into its disengaged state.
However, such an automatic control mechanism does not generally possess the sensitivity of operation of the foot upon a pedal, whilst it necessitates the development of fairly high power.
Similar remarks apply to the control mechanism of a speed variator, for example with variable-spaced pulleys and belt, in which the spacing of the pulleys in subject to the action of diaphragms and can be modified by an opposing means which is required, by the effect of force, to overcome the elastic resistance of the diaphragm.
Whatever the field of application, the exertion in an automatic control mechanism of a considerable power comparable to that of a manual control mechanism involves, for the driving means and their accessories, considerable dimensions, a high expenditure of energy, and difficult conditions to activate and de-activate the driving means, all without the benefit of comparable sensitivity to that of a manual control mechanism.
This invention relates to a control mechanism for a coupling device such as a clutch, a speed variator, a brake et cetera, which is free of these disadvantages and which is adapted to be automated, with low power and high sensitivity, in a simple construction of small dimensions.